Automatic telephone system



July 24, 1923.

W. T. POWELL I AUTOMATIC TELEPHONE SYSTEM Filed Aug. 3

1920 2 Sheets-Sheet 1 IU Lz/w MTI INVENTOR \AHHFEED T POWELL,

- BY 40 W ATTORNEY July 24, 1923. 11,462,8119

W. T. POWELL AUTOMATIC TELEPHONE SYSTEM ATTbRNEY Patented July 24, 1923.

wmrnnn 'r. POWELL, or uocnns'rnn, unw YonK,

- titans rates.

Assreuon TO THE STROMBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, OFROCHESTER, NEYV YORK,

A CORPORATION OF YORK.

AUTOMATIC TELEPHONE SYSTEM.

Application filed August 31, 1920. Serial no. 407,173.

' To (ZZZ whom it may concern:

Be it known that l, lV1NFRED.T. POWELL, acitizen of the United States,residing at lttochester, in the county of Monroe and State of New York,have invented certain new andv useful Improvements in Automatic.Telephone Systems, of which the following isa iull, clear, concise,an'dexact description.

This invention relates. to automatic telephone systems, and morepart-icularly to the circuits of non-numericalswitches employed in suchsystems. i g l It has been found that it is more economical of apparatusin automatic telephone sys tems when the groups in which these pieces ofapparatus are so arranged','are of large size, since in this manner agroup of apparatusis common to a larger number of subscribers.

Informer telephone systems the number of switches to which eachindividual nonnmnerical line switch has access has been 'limited owingto the amount of time consumed by the line switch in hunting over alarge group of trunkshaving access to automatic switches.

In accordance with the present inrent-ion it is. proposed to have alarge number of trunks terminate at each line switch, so that eacl'isubscriber may have access to a large group of automatic switches, andit is further proposed to arrange the circuits of the line switches sothat two difi erciiit trunks are simultaneously tested. In this way thehunting" of idle trunks is aca'complished in half the time previouslyconsumed.

In the drawings, 1 represents a por tion of a telephone system in whichthat part of the drawing at the left of the dotted line representsajsubscribers line with its individual lineswitch. The rectangle shownat the upper right'of- Fig. 1 represents one trunk and a very smallportion of the cirrcpresents a subscribers line with the line cuits ofthe numerical switch to which this trunk has access. At the lower righthand corner there is similarly represented a second; trunk. Fig. 2represents a modified form of the invention which diagrammaticallyswitch individual. thereto." In this'arraiigeinent it is assumed thatthere are fifteen trunks: in each group. i

The structure of the line switch employed in this invention may besubstantiallysimilar to that disclosed in the patent to Clement,#1,107,153, patented Aug. 11, 1914:, except that the switch will bedesigned for a larger number of brushes or wipers, andcooperatingsets ofcontactsthan disclosed in that patent. The sets of terminals of twotrunks maybe placed one above the other, and two sets of brushes may beplaced one above the other to operate with these sets or contacts. It isalso tobe understood that all the trunks to which the line switch hasaccess, may be arranged in one plane in the arc of a circle, and thatthe switch will then be provided with two sets of brushes arranged atsuch an angle to each other that they will simultaneously test differenttrunks at the same time.

In the course of the description of the so called stay-put lineswitchcircuits of Fig. 1, reference will be made to the well knowninterlocking arrangement between the line and cutoff relays,-such as isdisclosed in the patent to Lamb, #1,193,160 patented 'August 1, 1916. i

It is'believed that the invention willbest be understood by describingthe method of operating the line switch on the initiation of a call.When the calling subscriber whose substation circuits are indicated at Aon Fig. 1 removes his receiver from its switchhook, the slowreleasingline relay 5 is operated in a circuit closed from groundedbattery, winding otthis relay, inner upper back contact and armature ofthe secondary cut-oll relay 6, inner upper back contact and armature ofthe primarycut-ofl relay 7, through the calling line and substationcircuits, lower armature. and back contact of relay 7, inner lowerarmature andback contact of relay 6 to ground. The line relay isoperated in this circuit and ttracts its armatures. At its upperarmature and contact 8, it applies a guardinn potential over conductor9, through lower-most back contact and armature of relay .6. through themultiple test terminals 10 of the group of connectors that have accessto the calling line. At the lower armaturesa'nd front contacts ottheline relay, break points are closed in the circuits of the motor magnet11 ot the line switch.

, Let it be assumed that both of the trunks being tested by the lineswitchare busy, in which case there will be a direct ground potential.placed on the test terminals, such as'l3 and 17 of these trunks. Suchguarding potential 'is applied in the following manner. Whenever a trunkcircuit is seized and being held during a connection, its slow releasingrelay such as ll and 24 isoper ated, and Withthe release controlling re'lays such as 14: and 24 of associated trunks operated, a circuit isclosed for relay 26 from grounded battery, lower armature and frontcontact of relay 14, left hand armature and front contact of relay 2 1-to ground. With the relays 1 1 and 2t-operated, a direct groundpotential is applied through the armature and front contact of relay 26,up per, armature and continuity spring of re- 7 lay 14 to test terminal13 and through the right hand armature and continuity spring of relay 2to the test terminal 17. The motor magnet 11 thus has two operatingcircuits closed for itself, the first extending from grounded battery,right hand winding, back contact and armature of this magnet, innerarmature and front contact of line relay 5, upper-most back contact andarmagroups of trunks until either one or both of the test brushes 12aiid16 encounter an idle trunk, whereupon the motor magnet will cease tooperate.

i Let it be assumed that the first idle trunk testedby either the testbrush 12 or 16 while the two sets of brushes are being simultaneouslyadvanced is that trunk whose test terminal is designated 17 This idlecondi tion will be indicatedyby the presence of battery potential on itstest terminal. The primary cut-ofi relay 7 will. therefore be operatedover a circuit extending from grounded battery, resistance, back contactand continuity spring of relay 24, testterminal 17, brush 16, conductor15, upper armature and back contact of cut-ofi" relay 7, inner frontcontact and armature of line relay 5, con ductor 22, winding of cut-offrelay 7, con-- ductor 9, contact 8 and upper armature of relay toground, and when. cut-01f relay 7 is onceoperated it will be heldenergized in a circuit extending from grounded bat-- tery, right handwinding of magnet 11, its back contact and armature, conductor 22,winding ofrelay 7, conductor 9, contact 8 and armature of relay 5 toground. -It

should be noted that as soon as the line relay, 5 is operatedanenergizing circuit for the cut-off relays L6 and 7 is closed, butthese relays are shunted by a circuit closed "for the motor magnet 11including the test conductors of busy trunks. It should also he pointedout'that the cut-oft relays 6 and 7 will operate in. series withthemotor mag net 11,;butthis last mentioned motor mag net will not operatein series'with a out-oil relay. As soon as the primary cut-oft relay 7is operated, it extends the calling line to the brusheslS and 19 of theline switch and through the terminals of the selected trunk through bothwindings of relay 23 in series to gIOl'l11dBCl" battery. The relay 23which may be the impulse or stepping relay-of the first selector switchattracts its armature and 111 turn closesa circuit for the slowreleasing relay 24. Thislast named relay on operating closes a holdingcircuit off relay 7 will be operated in the manner just described, andthe secondary cut-cit relay 6 will be operated in a circuitextendingfrom grounded battery, resistance, upper contact and. continuity springof relay 1 1, test terminal 13, test brush 12, upper-- most armature andback contact of relay 6, lower-most front contact and armature of linerelay 5,.winding o1 the cut-ofi relay 6, and upper contact and armatureof line relay 5 to ground. The operation of the primary cut-offrela-y'7- prevents the extension of the calling line to the brushes and21, and thus prevents the energization of the impulse relay with theresult that the slowreleasing relayla is not operated to, apply holdingground on the terminal 13, so that thesecondary cut-01f relay 6 deenergizes shortly after this operation when line relay 5 deenergizes.

At the termination of the connection the holding ground will be removedfrom termi: nal 17 with the result that the cut-off relay 7 deenergizesand disconnects the calling line from the line switch brushes 18 and 19which have just been used in this connection. It will be. recalled thatthe line switch employed in the circuit of Fig. 1 is o f the stay puttype, that is; remainsv in engagement with the trunk terminals lastused, so that at the time of release it is only necessaryto disengagethe line switch brushes from the is seized as'a called line overthBCOllIlGC- tor terminals appearing'at the lower left otFig. 1, acircuit is closedfrorn ground at the connector switch (not-shown)thathas seized this line, conductor 10, lowermost armature and contactof relay 6; winding of cut-off relay 7, CQIlClllCtORQQ, armature backcontact and winding of motor magnet 11 to grounded battery. The magnetll -does-not I operate at this time but relay 7 is actuated.

It has been pointed out that'line relay and cut-oft relay .7 areinterlocking, that is, if line relay 5 has its armature attracted whenrelay 7 is energized then this lastmentioned relay-fully attracts itsarmature to disconnect the line relay from theline and. to extend thisline to brushes ofits 11116 switch lflhowever, cut-off relay 7 alone. isoperated its armature is attracted] only enough todisconnectline relay 5from the line. 7 Thus when a line is called'its line relay'is disabledand it is not extended through its line switch to .an idle trunk;

; Th circuit arrangementshown inFig. 2 is similar to that disclosed inFig. 1. except that in Fig. 2 an advance to normal switch having twosets of brushes with tour brushes in each set is used, whereas in .thearrange mentshown-in Fig. .1 the switch is of that type which remains inengagement with the trunk last used and is provided with two sets ofbrushes.-- of. three brushes in each set.

It is believed thatthe operation of the line switch circuitsof Fig; 2will best be. understood by describing the method of initiating a call.When the subscriber at B removes his. receiver fromits switchhook, theslow releasing line relay is energized in a circuit traceable fromgroundedbattery, winding of this relay, inner lowerback contact andarmature of the secondary cut-oif relay 51. inner lower back contact andarmature of the primary Cllt'rOff relay 52, through the callingsubscribers line and substatlon -cir cuits. inner upper armature andback contact of relay 52, inner upper armature and "backcontact ofrelay51 to ground. The line relay on energizing closesan initial energizingcircuit for motor magnet 53., through oil normal contact 54;. armatureand front contact of line relay 50. conductor 55, back contact andarmature of the motor magnet and resistance to grounded battery. Un-

der the control of thisfeircuit the motor magnet advances its brushesinto engagement with the first two trunks terminating at the switch. Inthe event that both of these trunks are busy, this condition will beindicated byabsence of ground potential on the test terminalscorresponding to and 56. VViththis conditiomthe primary cutoff relay52and the secondary cut-off relay 51 will remain inactive and asubstitute operating circuit for the lhotor magnet 53 will now be closedfromground, winding 01" this ma -net. of? normal contacts 57 lowermostbackcontacts and armaturesoi relays 51 and 52, back contact and armatureof the motor magnet, and resistance to grounded battery. Under thecontrol of this circuit the switch advances its sets of brushes over theterminals of busy trunks until an idle trunk such as #2 is reached. Thisidle trunk is characterized by the. presence of ground potential on. thetest terminal 58,

this circuit and extends the calling line to the line switch brushes 61and 62, over conductors 63 and 64 An impulse relay (not shown)associated with the numerical. switch of trunk #2. will thereupon beenergized in a circuit including both sides of the se lected trunk andboth sides of the calling line in series. .111 response to the operationof this impulse relay a release relay, (not shown) isoperated toapply aholding battery to the holdingterminal 65 of trunk #2. holding brush 66,conductor 67, upper winding, front contactwand armatur of the cut-offrelay 52 to .ground. In the event that the test terminals 58 and 59 oftrunks #2 and. #17 which. it is assumed are being simultaneously testedare idle, both of the cut-oil relays 5]. and 52 will be energized. Thecut-olf relay. 52 being energized over the circuit previously describedand thecutofl relay 51 being operated in a circuit completed fromground, at test terminal 59., test brush 68. lower winding of? thecutoff relay .5l..armature and front contact of relay 50.

'to provide the application of holding battery tojthe holding terminal72 of trunk 17. Also at the upper-mostarm a ture and back contact of theprimary cut-ofl relay 52 the ho d ng circuit of the relay 51 is opened.

At the termination of the connection the holding battery is removed fromthe holdterminal of the selected trunk. such as terminal. 5 of trunk #2;thereupon the locl-nngc rciut of primary cutcfl relay 52 is opened, andthis relay retracts its armatures. An operating circuit is thuscompleted for the motor magnet 53 to advance the brushes of the lineswitch to normal position. This operating circuit extends from ground,winding of the motor magnet, off

normal contacts 57,1ower-most back contacts-and armature of relays 51and 52, contact and armature of themotor magnet and resistance togrounded battery. Under "the control of this circuit the motor magnetadvances the line switch to its normal posi- -t1on,'at which time the onnormal contacts '57 are opened andthe normally closed contacts 54 areclosed in readiness for another 1. In a telephone system, a subscribersline, a" plurality of trunks arranged in groups,

an automatic nOn numerical switch for the;

use of said line, means for causing said switch to simultaneously test atrunk in each group, means for preventing the seizure by said switch ofmore than one of the trunks "which are being simultaneously tested, and

releasing means for said switch.

2, In a telephone system, a subscribers line a luralit of trunks arraned in 4 y h jgroups, an automatic non-numerical switch for the use ofsaid line, means for causing said switch to simultaneously test a trunkIn each group, means for preventing the se zure by said switch of morethan one of the trunks which are being simultaneously tested, a holdingcircuit'completed over each trunk selzed, and means for preventing thecompletion ofmore than one holding circuit simultaneouslyin each switch.

3. In a telephone system, asubsc'ribers line, a. plurality of trunksarranged in groups, an automatic non-numerical switch for the use ofsaid subscribers line, means for causing said switch to simultaneouslytest a trunk in each group, a cut-off relay for each group of trunksarranged to be s1- multaneously tested, said cut-ofl relayscontrollingthe seizure of a trunk by said line switch, and means forpreventing more than 'one'cut-ofl relay from seizing a trunk at the sameswitch. i

4. In atelephone system, a subscribers line, a plurality ofjtrunksarranged in groupsan automatic non-numerical switch individual to saidline,means for causing said switch to simultaneously test a trunk ineach'group, means including primary and secondary .cut-ofi' relays forthe groups for controlling the seizure and holding of idle trunks, meanscontrolled by said primary and said secondary c'ut ofli relays forpreventing the holding of more than one trunk.

55, In a telephone system, an automatic noni'numerical switch havingfixed terminals and movable brushes, a plurality of groups of trunksterminating in groups of fixed terminals' at said switch, a subscribersline arranged to be connected to a plurality of sets of brushes, meansfor causing said sets of brushes to simultaneously test a plurality ofgroups of trunks, a plurality of relays arranged to'be variablyopera-ted dependent on the groupsjin which a trunk is seized, meansforconnecting said subscribers line to one set of brushes at front contactsof one of said'relays andto the other set of brushes throughbackcontacts of said last mentioned relay, and means for operatingone'of said relays over a seized trunk.

'6. In a telephone system, a subscribers line, a plurality of trunksarranged in groups, an automatic non-numerical switch provided withfixed terminals in which said trunks terminate, and with two sets ofbrushes individual tosaid subscribers line,

l 7; In a telephonesystem, a subscribers line, "a plurality of trunksarranged in groups. an automatic switch individual to said subscribersline, for extending said line to anyof said-trunks, means including aline relay energized over said subscribers line for causing saidautomatic switch to simultaneously test a trunk in each group, meansincluding'primary andsecondary cut-ofi' relays for the? groups of trunksfor controlling the seizure and the holding of idle trunks, and

means controlled by said primary and said secondary cut-off relays forpreventing the holding of more than one trunk said last mentioned" meansincluding an operating circ'uitfor said primary and secondary cut offrelays completed at said line relay.

8; In a telephone system, a subscribers line, plurality of" trunksarranged in groups, an automaticswitch individual to said line, a linerelay energized over said subscribers line, a motor magnet controlled bysaid line relayfor causing said switch'to :simultaneously'test a trunkin' each group, a cut-off relay for each" group of trunks,

means responsive to the testing of an idle trunk for operating one ofsaid cut-off relays to seize an idle trunkinits associated group oftrunks and conductors for said subscribers line by which to seize saidline as a calledline, one of said. conductors serially including" awinding of one of said cut-off relays. l i

9. In a telephone system, a subscribers line,"a plurality of trunks.arran ed 'in groups, an automatic switch individual to said line, asingle wound line relay, means including a circuit extending over thetwo sides of said subscribers line in series for operating said linerelay, a motor magnet for causing said autOmatic switch tosimultaneously test a trunk in each group, a circuit "for said motormagnet controlled by said line relay and means responsive to the testingof an idle trunk for seizing the same and for disabling said line relay.

10. In a telephone system, a subscribers line, a plurality of trunksarranged in groups, an automatic switch individual to said line, a linerelay energized over said incoming line, a double wound motor magnet forcausing said automatic switch to simultaneously test a trunk in eachgroup, circuits for said motor magnet, each including a winding of saidmotor magnet and controlled at said line relay, and means for seizing anidle trunk in one of said groups of trunks as soon as it is tested andfor disabling said line relay.

11. In a telephone system, an automatic switch having fixed terminalsand sets of movable brushes, a plurality of groups of trunks terminatingin groups of fixed terminals, a subscribers line arranged to beconnected with a plurality of sets of brushes, a line relay operatedover said incoming line, a double wound motor magnet for advancing saidbrushes over said fixed terminals a test conductor for each trunk,operating circuits for said motor magnet each serially including awinding of said motor magnet, contacts of said line relay and a testconductor of the trunk being tested, and means responsive to the testingof an idle trunk for seizing the same and for interrupting the operatingcircuits of the motor magnet.

12. In a telephone system, a subscribers line, a plurality of trunksarranged in groups, an automatic switch provided with fixed terminals inwhich said trunks terminate and with sets of movable brushes in whichsaid subscribers line terminates, a double wound motor magnet foradvancing said brushes to test a trunk in each group simultaneously, aline relay energized over said incoming line, a cut-off relay for eachgroup of trunks operating to disable said line relay, a test conductorfor each trunk, operating circuits for said motor magnet, seriallyincluding the windings of said motor magnet, contacts of said linerelay, contacts of said cut-off relays and test conductors of trunksbeing tested, and a circuit for each cut-ofi relay serially including awinding of said motor magnet, the winding of the cutoil relay andcontacts of said line relay, said last mentioned circuit being disabledby one of said operating circuits for the motor magnet during theoperation of said switch, and a holding circuit for an actuated cut-ofl'relay. i

In witness whereof, I hereunto subscribe my name this 24th day ofAugust, A. D. 1920.

WVIN FRED T. POWELL.

